Single faced corrugated board is manufactured by gluing a liner to a corrugated medium under controlled conditions. A web of core material to be corrugated is passed through a pair of counter-rotating corrugating rollers. After the corrugated core leaves the corrugating rollers, a paste applicator applies an adhesive to the peaks of the corrugations. A web of liner material is faced to the pasted peaks of the corrugated material by a pressure roller co-operating with one of the corrugated rollers. The final product is a single faced corrugated board having the liner on one side of the corrugated core.
A common problem in manufacturing single faced corrugated board is maintaining the corrugated core flush against the corrugating roller as the roller rotates to carry the corrugated core to the nip between the corrugating roller and the pressure roller, where the liner is applied. The resilience of the core and centrifugal force caused by rotation of the corrugating rolls tends to cause the core to separate from the corrugating roller before it enters the nip, leading to bulges, wrinkles, poor liner adhesion and numerous other problems. Some attempts to solve this problem rely on mechanical devices to physically hold the core against the corrugating rollers. Some approaches use suction to hold the core against the rollers. Another method commonly used is to enclose the corrugating rollers, pasting unit and pressure roller in a chamber which is pressurized by air to a pressure sufficient to hold the core against the corrugating rollers. This approach eliminates problems with mechanical or vacuum systems, but requires the chamber to be sealed against excessive air leakage so that the desired pressure can be maintained in the chamber. In these systems, a seal roller is used in cooperation with the pressure roller. The liner passes between the seal roller and the pressure roller, sealing the entry point of the liner into the chamber. A seal assembly is required on the back side of the seal roller to prevent air leakage between the chamber and the surface of the seal roller.
Two types of seal assemblies are commonly used in this type of apparatus. The first type of seal assembly is a fixed beveled brass seal bar. The bar is mounted between the seal roller and the chamber. However, the beveled bar has many disadvantages. The bar cannot tolerate any thermal expansion relative to mating parts. Another problem occurs if the seal roller's surface is uneven, or has an out of round condition, because there will be a tendency for the roller to be obstructed by the seal bar. This could lead to excessive and uneven wear of the seal bar or the seal roller. In addition, there is no way to easily adjust the position of the bar.
The second type of seal assembly uses a cantilever-mounted, flexible spring steel blade having a brass wear strip attached to its outer edge. The flexible blade is bolted to a fixed structure of the apparatus. The blade is then extended in an upward direction at a 45.degree. angle until it makes intimate contact with the seal roller. Unfortunately, the flexible spring steel strip assembly is almost invariably too flexible and unstable by its very nature, which results in an assembly which has a short service life and must be frequently replaced.
It is therefore an object of the invention to provide a floating seal assembly which effectively seals the pressure chamber of a positive-pressure single faced and which avoids the problems of known seals.